Gas-blast circuit breaker having dual piston means providing double-acting puffer arrangement



y 1967 s. A. MILIANOWICZ 3,331,935

GAS-BLAST CIRCUIT BREAKER HAVING DUAL PISTON MEANS PROVIDING DQUBLE-ACTING PUFFER ARRANGEMENT Filed Dec. 21, 1964 5 Sheets-Shee 1 H II FIG. I.

WITH CONTROL VALVES I DOUBLE ACTION F G. 3.

PUFFER PRESSURE UNCONTROLLED TIME WITNESSES INVENTOR SMIWJ'Z/QA/ 4. ll/UAA/Ohl/CZ ATTORNEY y 1967 s A. MILIANOWICZ 3, 3 3

GAS-BLAST CIRCUIT BREAKER HAVING DUAL- IISTON MEANS PROVIDING DOUBLE-ACTING PUFFER ARRANGEMENT Filed Dec. 21, 1964 5 SheetsSheet 2 FIG.'2.

July 18, 1967 S. A. MiLIANOWICZ GAS-BLAST CIRCUIT BREAKER HAVING DUAL PISTON MEANS PROVIDING DOUBLE-ACTING PUFFER ARRANGEMENT 5 Sheets-Sheet 3 Filed Dec. 21, 1964 FIG. 4.

FIG. 5.

July 18, 1967 s. A. MILIANOWICZ 3,331,935 GAS-BLAST CIRCUIT BREAKER HAVING DUAL PISTON MEANS PROVIDING DOUBLE-ACTING PUFF'ER ARRANGEMENT Filed Dec. 21, 1964 5 Sheets-Sheet 4.

FIG. 6.

July 1967 s. A. MILIANOWICZ 3, 5

REAKER PIS GAS-BLAST CIRCUIT B HAVING DUAL TON MEANS PROVIDING DOUBLE-ACTING PUFFER ARRANGEMENT Filed Dec. 21,. 1964 5 Sheets-Sheet 5 FIG. .7.

United States Patent 3,331,935 GAS-BLAST CIRCUIT BREAKER HAVING DUAL PISTQN MEANS PROVIDING DOUBLE-ACTING PUFFER ARRANGEMENT Stanislaw A. Milianowicz, Penn Hills, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Dec. 21, 1964, Ser. No. 419,784 19 Claims. (Cl. 200143) This invention relates generally, to circuit breakers and, more particularly, to gas-blast circuit breakers having interrupters of the puflfer type.

Circuit interrupters of the puffer type utilize a fixed cylinder with a moving piston, or a fixed piston with a moving cylinder, as a means of compressing a gas which is then directed into the vicinity of an electric arc to interrupt the arc. Prior interrupters of this type have certain limitations with respect to the maximum pressure generated in the puffer cylinder and the time at which the maximum pressure occurs during the process of circuit interruption.

An object of this invention is to overcome the foregoing limitations by providing means for obtaining a higher pressure, which occurs earlier in the interrupting cycle, than obtained with prior putters.

Another object of the invention is to provide for varying the maximum pressure and the time at which it occurs in a putter for a circuit interrupter.

A further object of the invention is to increase the duration of time during which a high differential pressure is maintained by the putter.

Still another object of the invention is to provide a cushioning effect on members of the putter during opening of the contact members of a circuit breaker.

A still further object of the invention is to provide a puffer which will function properly during a close-open operation of a circuit breaker.

Other objects of the invention will be explained fully hereinafter, or will be apparent to those skilled in the art.

In accordance with one embodiment of the invention, higher gas pressure in a circuit interrupter of the putter type is obtained by providing a double-acting puffer having a primary piston and a secondary piston which are spring driven toward each other in the same cylinder during the first part of the interrupting operation, thereby obtaining a higher differential pressure in a shorter time than could be obtained with a single piston. A system of valves increases the duration of time during which the high differential pressure is maintained, and also provides a cushioning effect on the primary and secondary pistons,

.which are actuated to a position at the end of the part of the interrupting opera-,

cylinder during the latter tion.

For a better understanding of the nature and objects of the invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a view, partly in section, and partly in elevation, of a circuit breaker embodying principal features of the present invention;

FIG. 2 is an enlarged view, primarily in section, of one of the interrupting units for the circuit breaker;

FIG. 3 is a View of curves showing operating characteristics of puffers of difierent types;

FIGS. 4 and 5 are views, primarily in section, of interrupting unit having modified contact arrangements;

FIG. 6 is a view, partly in section and partly in elevation, of a modified arrangement of the putter members of an interrupter; and

FIG. 7 is a View, similar to FIG. 2, of a modified interrupter.

ice

Referring to the drawings, and particularly to FIG. 1, the circuit breaker shown therein comprises a metal tank 10, two terminal bushings 11 which extend through the top of the tank 10, two circuit interrupting units 12, which are mounted inside the tank on the lower ends of the terminal bushings 11, a conducting crossbar 13, which connects the interrupting units 12 in series when in the closed-circuit position, an insulating lift rod 14 for raising and lowering the crossbar 13, and an operating mechanism which may be of a type well known in the circuitbreaker art, and may be enclosed within a housing 15. The tank 10 contains any suitable interrupting gas, such as sulfur hexafiuoride (SP gas, or even air, for certain applications. Only one pole-unit is shown in FIG. 1. It will be understood, however, that additional pole-units may be provided, as required. Thus, for a three-phase system, three pole-units would be provided. Each pole-unit may be mounted within a separate tank, or all three pole-units may be mounted within one tank, if desired.

As shown in FIG. 2, each interrupting unit 12 comprises an upper closure support plate 16, a puffer cylinder 17, a support member 18, a lower movable disconnecting contact 19, an accelerating spring 21, a fixed post-type stationary contact member 22, a primary piston 23, and a secondary piston 24 disposed inside the puffer or operating cylinder 17. In addition, the unit 12 includes a movable contact assembly 25 and a vent nozzle, or orifice 26 carried by the primary piston 23, a conducting operating rod 27, which connects the lower movable disconnecting contact 19 with the movable assembly 25. There is also provided a secondary piston spring 28, which biases the secondary piston 24 upwardly, and a latching mechanism 29, which retains the secondary piston 24 in its lowermost, or initial position within the cylinder 17. A boss 31, which may be an integral part of the upper conducting closure support casting 16, may be threaded onto the lower end of one of the terminal studs extending through the terminal bushing, thereby supporting the interrupting unit 12. The operating puffer cylinder 17 is preferably composed of a suitable insulating material, and its upper end may be threaded into the upper support casting 16. The lower end of the operating cylinder 17 may be threaded into the support member, or casting 18. The accelerating spring 21 is disposed between a shoulder 18a on the support member 18 and the lower movable disconnecting contact 19 to bias both the movable disconnecting contact 19 and the primary piston 23 downwardly. The spring 21 is compressed when the primary piston 23 is in its uppermost position within the operating cylinder 17, and the movable contact assembly 25 conductively engages the fixed contact member 22, which is attached to the upper closure plate 16.

The movable contact assembly 25 comprises contact fingers 32, which engage the fixed contact member 22, and a centraly-located arc horn 34. The lower end of the arc horn 34 may extend through the base for the fingers 32, and also the primary piston 23, and may be threaded into the upper end of the conductive operating rod 27, thereby attaching the primary piston 23 and the movable contact assembly 25 to the operating rod 27.

The vent nozzle, or orifice 26 is preferably composed of polytetrafiuoroethylene, generally known under the trade name Teflon. The nozzle 26 may be threaded onto the upper end of a cylindrical projection 35 aflixed to the primary piston 23. An opening 36 extends through the primary piston 23 and into the interrupting nozzle 26.

The conducting operating rod 27 extends through the secondary piston 24, the support member 18, and the latching mechanism 29. The lower end of the operating rod 27 is attached to-the bottom lower movable disconnecting contact 19 in any suitable manner, as by being threaded into the disconnecting contact plate 19. A suitable seal 37 may be provided around the operating rod 27 to prevent compressed gas from escaping around the operating rod 27 where it passes through the secondary piston 24. The secondary spring 28 is disposed between a shoulder 38 on the lower end of the support member 18 and a collar 39 affixed to the bottom of the secondary piston 24.

A sleeve 41 extends downwardly from the secondary piston 24. The upper end of the sleeve 41 may be threaded onto the collar 39. The lower end of the sleeve 41 has a horizontal projection 40 thereon, which is engaged by three latches 42, each of which is pivotally mounted on a projection 43 on the support member 18 by means of a pivot pin 44. Each latch 42 is biased into latching engagement with the sleeve 41 by a compression spring 45. A link, or hook 46 is pivotally attached to each latch 42 by means of a pivot pin 47. A leaf spring 48 biases each hook 46 toward a release arm 49 which extends upwardly tromthe lower movable disconnecting contact 19.

In order to maintain a high pressure differential generated by the putter for a period of at least one cycle of a 60-cycle Wave, a control valve arrangement 50 is provided in the secondary piston 24 and in the support member 18. A valve plate 51 is disposed to cover openings 52 extending through the secondary piston 24. The valve plate 51 is retained in the secondary piston by a retainer ring 53, which may be threaded onto a collar 54 formed with the secondary piston 24.

A flanged cylindrical valve 55 is disposed to close an opening 56 between the support member 18 and the sleeve 41 on the secondary piston 24. The valve 55 may be biased to its closed position by a plurality of relatively light compression springs 57 disposed between the support member 18 and a retaining ring 58, which may be threaded onto the cylindrical portion of the valve 55. A plurality of openings 59 are provided in the retaining ring 58. A suitable seal 61 may be provided between the cylindrical portion of the valve 55 and the sleeve 41, which is attached to the collar 39 on the secondary piston 24.

As shown in FIGS. 1 and 2, the interrupting unit 12 is shown in the closed-circuit position with the contact members 22, 25 closed. The primary piston 23 and the lower movable disconnecting contact 1-9 are held in their uppermost positions against the force exerted by the accelerating spring 21 by means of the cross-arm 13, which is connected by the lift rod 14 to the trip-free operating I mechanism enclosed in the housing 15.

When the mechanism supporting the moving disconnecting contact 19 is tripped, the moving disconnecting contact 19 and the primary piston 23 are driven downwardly by the accelerating spring 21. Simultaneously with the commencement of the motion of the primary piston 23, or at any predetermined time lapse, depending on the relative positions of a projection 63 on the release arm 49 and a tooth portion 62 of the hook 46, the projection 63 on the release arm 49 engages the tooth 62 of the hook 46, which pulls the latch 42, by means of the pin 47, to rotate the latch 42 about its pivot pin 44 to thereby disengage the latch 42 from the projection 40 on the lower end of the sleeve 41. This permits the secondary piston 24 to be driven upwardly by the secondary spring 28. When thelatch 42 is rotated about its pivot point by the hook 46, a projection 64 on the hook 46, which normally engages the latch 42 except during closing of the breaker, causes the hook 46 and'the latch 42 to move as a unit, thereby rotating the hook 46 about the pivot pin 44 to disenagage the tooth portion 62 on the hook 46 from the projection 63 on the release arm 49 which permits the movable disconnecting contact 19 and the primary piston 23 to continue with their downward opening motion. A stop 65 on the projection 43 limits the movement of the latch 42 clockwise after it is disengaged from the projection 40.

In this manner, the primary piston 23 and the secondary piston 24 are driven toward each other within the operating cylinder 17, thereby compressing the gas contained within the operating cylinder between the two pistons. This action increases the rate at which gas is being compressed and peak pressure is reached earlier than in a conventional fixed lower cylinder.

When the secondary piston 24 is released and begins to move toward the primary piston 23, the piston valve 51 closes, permitting pressure to build up within the cylinder between the primary and the secondary pistons, and the bottom valve opens, permitting gas to enter the cylinder between the bottom casting 18 and the secondary piston 24. Gas compressed between the two pistons fiows through the opening 36 and the interrupting nozzle 26 to extinguish the arc drawn between the fixed contact member 22 and the movable contact assembly 25.

When the pressure within the operating cylinder 17 between the primary and the secondary pistons reaches such value as to retard the secondary piston 24 to zero velocity and overcome the force exerted by spring 28, the secondary piston 24 starts to move away from the primary piston 23 under action of the compressed gas and while the piston valve 51'remains closed, the bottom valve 55 will now close since the gas contained between the secondary piston 24 and the support member 18 is now being compressed. Both valves 51, 55 will remain closed until the pressure of gas between the secondary piston 24 and the support member 18 exceeds the pressure between the secondary and the primary pistons. The piston valve 51 will now open and gas will enter the space between the two pistons, thereby adding to the quantity of gas available at the beginning of the opening operation. The motion of the primary piston 23 will continue with the piston valve 51 open and the bottom valve 55 closed until the opening operation is completed.

During the time when both valves 51 and 55 were closed and the secondary piston 24 was compressing the gas contained between itself and the bottom support member 18, the secondary piston was being decelerated, or cushioned with a shock-absorbing action, which resulted in reducing or removing a sharp pressure drop in the main cylinder as shown by the curves in FIG. 3. Thus, the high differential pressure produced by the putter is maintained for a longer period of time than would be the case without the control valves 51, 55.

Another advantage of the present valve arrangement is the increased amount of gas available in the putter cylinder 17 for a close-open operation. While closing the breaker, the cylinder is being filled with gas not only through the nozzle 26 but also through the two valve members 51 and 55, which both remain open during the closing operation. This action facilitates refilling the cylinder 17 and on an immediate tripping operation, starting pressure in the puffer cylinder 17 will be considerably closer to maximum, or tank pressure than is the case with any type of pufier without the valves.

As previously explained, the secondary piston 24 normally is retained in its lowermost or initial position by the latching mechanism 29. When the contact members are fully opened, with the primary piston 23 and the movable disconnecting contact 19 in their lowermost positions, the accelerating spring 21 is expanded, and the secondary spring 28 is compressed. The relation between the accelerating spring 21 and the secondary spring 28 is such that at any point on the operating stroke, the force exerted by the spring 21 is greater than that of the spring 28. This characteristic permits the secondary piston assembly 24 to reset on slow opening, as during maintenance or assembly of the breaker.

When it is desired to close the breaker, the operating mechanism is utilized to raise the crossarm 13 and the movable disconnecting contact 19, thereby raising the primary pistons 23 and closing the contact members 22, 25 of the breaker. The accelerating spring 21 for each interrupter 12 is compressed during the closing operation. During the closing operation, the release arm 49 pushes the cam end of the link, or hook 46 against the leaf spring 48, and the hook 46 rotates about its pivot pin 47 to permit the release arm 49 to move past the tooth portions 62 on the hook 46. The hook 46 is provided with two or more teeth 62, only two being shown in the drawing. In practice it will have a number of teeth in order to permit the release arm 49 to engage it at more than one position. This feature is required during a close-open operation when the breaker may be tripped to open before the closing operation is completed, that is before the moving disconnecting contact 19 and the primary piston 23 are raised to their uppermost position by the crossarm 13.

As previously mentioned, the time at which peak pressure occurs within the putter cylinder may be determined by the distance between the uppermost tooth 62 on the hook, or link 46 and the projection 6-3 on the release arm 49. This distance determines the time when the secondary piston is released to travel upwardly within the cylinder 17 toward the downwardly-moving piston 23, thereby determining the time when the maximum pressure of the gas between the two pistons 23, 24 is obtained.

Heretofore, in gas-blast circuit breakers dual pressure systems only were capable of supplying sufiicient amounts of gas at such a rate as to maintain the pressure differential necessary for successful interruption of a high-power electric arc in an interrupter of a hollow contact type. It was recognized that prior putters could not perform satisfactorily with hollow contact interrupters of the type described in US. Patent No. 3,154,658, by R. G. Colclaser, Jr., and R. N. Yeckley, and assigned to the Westinghouse Electric Corporation. From an anlysis of the double-action valve-controlled puffer hereinbefore described in conjunction with a double hollow contact interrupter it is apparcut that this pufier can develop suflicient pressure differ ential lasting for. a long enough period of time to interrupt short circuit currents of a magnitude presently interrupted by hollow contact interrupters in dual pressure breakers.

A double hollow contact interrupter and double action valve-controlled pufier are shown in FIG. 4 in which like parts are designated by the same reference characters as in FIG. 2. The structure shown in FIG. 4 is similar to that in FIG. 2 with the exception that the stationary contact member 22', the horn 34' and the conducting operating member 27' are of a hollow construction. Openings 66 and 67 are provided in the upper plate 16' and the lower .plate 19', respectively, for receiving the ends of the members 22' and 27', respectively. Thus, gas compressed between the primary piston 23 and the secondary piston 24 in the manner hereinbefore described flows through the opening 36 into the hollow contact member 22' and the hollow arc horn 34 and hollow member 27 to extinguish the are drawn between the fixed contact member 22 and the movable contact assembly 25. The arc transfers from the contact fingers 32 to the arc horn 34 and the inside of the hollow contact member 22'. The control valves 51 and 55 function in the manner hereinbefore described to maintain the high differential pressure produced by the pufifer for a sufiicient length of time to interrupt the arc.

The single hollow contact arrangement shown in FIG. 5 is similar to the arrangement shown in FIG. 4 with the exception that the arc horn 34 is of a solid construction and blocks the entrance to the hollow conductor 27 Thus, the compressed gas is forced through the opening 36 and into only the hollow contact member 22' during the interrupting operation. The are transfers from the fingers 32 to the arc horn 34" and to the inside of the hollow member 22. The insulating member 26' directs the flow of gas into the hollow member 22 to extinguish the arc. The pistons 23 and 24, the latching mechanism 29 and the valves 51 and 55 function in the manner hereinbefore described.

The modified interrupting unit 12' shown in FIG. 6 comprises a generally cylindrical metal housing 71 and two I insulators 72 and 73 attached to the housing 71 in a suitable manner. A conducting closure plate 74 is attached to the outer end of the insulator 72 and another conducting closure plate 75 is attached to the outer end of the insulator 73. Current transformers 76, 77 and 78 may be mounted on the housing 71. Electrical conductors (not shown) may be connected to the plates 74 and 75. The housing and the insulators may be filled with an interrupting gas, such as SP A stationary contact member 22 is attached to the plate 74. A cluster of contact fingers 32 and a generally cupshaped shield 79 are attached to a movable conducting member 27 by an arc horn 34. A nozzle or orifice 26' may be threaded into the shield 79. The nozzle 26' is preferably composed of polytetrafiuor-oethylene. The contact fingers 32 engage the contact member 22' when the member 27 is in its uppermost or closed position.

The piston 24 is movably mounted on the member 27 inside a puffer cylinder 17' having a closure plate or head 81 threaded into its upper end. The head 81 is composed of insulating material which may be formed around the base of the shield 79. Thus, the head 81 is attached to the member 27 so that the member 27' is movable with the cylinder 17'. The lower end of the member 27 is engaged by contact fingers 82 attached to the conducting plate 75.

A bifurcated operating lever 83 is connected to a band 84, secured to the cylinder 17', by links 85, only one of which is shown. The lever 33 is oscillated by a shaft 86 which may be driven by a suitable operating mechanism, such as a compressed air mechanism (not shown). Thus, when the shaft 86 is rotated counterclockwise, the cylinder 17, the conducting member 27' and the movable contact assembly 25 are moved downwardly if the interrupter is mounted vertically or to the right if mounted horizontally.

When the member 27 is moved downwardly, a release arm 49', attached to the member 27, releases the latching mechanism 29 to permit the spring 28 to drive the piston 24- upwardly in the manner hereinbefore described. Thus, gas is compressed between the cylinder head 81 and the piston 24 and forced through the opening 36' and out through the nozzle 26' to extinguish the are drawn between the movable contact assembly members and the stationary contact member when they are separated. The piston 24 is returned to its initial position by the compressed gas as explained hereinbefore. Likewise, the valves 51 and 55 function in the manner previously described. The movement of the cylinder 17 is guided by a guide cylinder 87 having a flange 88 thereon which is attached to a plate 89 at the lower end of the housing 71. The cylinder 87 also supports the support member 18' which supports the latching mechanism 29 and the spring 28. The lower end of the conducting member 27 is guided by the contact fingers 82. As previously explained, the upper end of the member 27 is attached to the shield 79 which is secured in the cylinder head 81.

The contact members of the interrupter are closed by rotating the shaft 86 clockwise to return the cylinder 17 to the position shown in the drawing. The cylinder 17' is returned in this position by the operating mechanism until released by a tripping device in a manner well known in the art. It will be understood that two or more interrupters of the type shown in FIG. 6 may be connected in series in a circuit breaker if desired and operated by the same operating mechanism.

The modified interrupting unit shown in FIG. 7 is similar to the unit shown in FIG. 2 except that the control valve arrangement 50 is omitted, thereby simplifying the structure and reducing its cost. While the simplified unit without the valve arrangement will not maintain the differential pressure produced by the puffer for as long a period of time as the unit having the control valve arrangement, the simplified unit is capable of successful operation at ratings which are above the capabilities of prior puffer interrupters.

In FIG. 7 like parts are designated by the same reference characters as in FIG. 2. In some cases the numerals are primed because the designed parts are located differently from FIG. 2. The function and mnner of operatio of the parts shown in FIG. 7 are similar to those described hereinbefore with reference to FIG. 2. Therefore, the description will not be repeated. The interrupting unit shown in FIG. 7 may be utilized for quick reclosing after opening since there is no decelerating action on the secondary piston 24 as it travels towards its initial position where it is latched by the latching mechanism 29' to permit reclosing of the contacts of the interrupter by returning the primary piston 23 to its initial position.

From the foregoing description it is apparent that the invention provides for increasing the maximum pressure obtainable within a puffer cylinder 17,013 a given size. Furthermore, the maximum pressure is obtained at an earlier time in the interrupting cycle. Also, the high-pressure differential generated by the puffer is maintained for a longer period of time than is possible with prior-type pufier devices. The advantages of the present puffer make it possible to interrupt higher currents, thereby enabling the rating of a circuit interrupter to be increased without increasing the size of the interrupter.

Since numerous changes may be made in the abovedescribed construction and different emboidments of the invention may be made without departing from the spirit and scope thereof, it is intended that all subject matter contained in the foregoing description, or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A circuit breaker comprising a tank containing an interrupting gas, at least two interrupter units disposed inside the tank, a conducting cross arm for connecting the interrupter units in series, each interrupter unit comprising a cylinder, a primary piston and a secondary piston disposed inside the cylinder, an accelerating spring for driving the primary piston in one direction from an initial position, a secondary spring for driving the secondary piston toward the primary piston from an initial position to compress gas between the piston, said secondary piston being returned to its initial position by the compressed gas, and means 'for raising the cross arm to compress the accelerating spring and return the primary piston to its initial position.

2. A circuit breaker comprising a tank containing an interrupting gas, at least two interrupter units disposed inside the tank, a conducting cross-arm for connecting the interrupter units in series, each interrupter unit comprising a cylinder, a primary piston and a secondary piston disposed inside the cylinder, means for driving the primary piston in one direction from an initial position, means for driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons, said secondary piston being returned to its initial position by the compressed gas, and means for raising the cross-arm to return the primary piston to its initial position.

3. A circuit breaker comprising a tank containing an interrupting gas, at least two interrupter units disposed inside the tank, a conducting cross-arm for connecting the interrupter units in series, each interrupter unit comprising a cylinder, a primary piston and a secondary piston disposed inside the cylinder, means for driving the primary piston in one direction from an initial position, meansfor driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons, said secondary piston being returned to its initial position by the compressed gas, latching means for retaining the secondary piston in its initial position, means for raising the cross-arm to return the primary piston I to its initial position, and means actuated by downward movement of the primary piston for releasing said latch ing means.

4. A-circuit breaker comprising a tank Containing an interrupting gas, at least two interrupter units disposed inside the tank, a conducting cross-arm for connecting the interrupter units in series, each interrupter unit comprising a cylinder, a primary piston and a secondary piston disposed inside the cylinder, an accelerating spring for driving the primary piston in one direction from an initial position, a secondary spring for driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons, said secondary piston being returned to its initial position by the compressed gas, latching means for retaining the secondary piston in its initial position, means for raising the cross-arm to return the primary piston to its initial position and compress the accelerating spring, and means actuated by downward movement of the primary piston for releasing said latching means.

5. A circuit breaker comprising a tank containing an interrupting gas, at least two interrupter units disposed inside the tank, a conducting cross-arm for connecting the interrupter units in series, each interrupter unit comprising a cylinder, a primary piston and a secondary piston disposed inside the cylinder, an accelerating spring for driving the primary piston in one direction from an initial position, a secondary spring for driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons, said secondary piston being returned to its initial position by the compressed gas, pivoted latching means for retaining the secondary piston in its initial position, means for raising the cross-arm to compress the accelerating spring and retain the primary piston in its initial position, and hook means pivotally attached to the latching means and actuated by downward movement of the primary piston to release said latching means.

6. In acircuit interrupter, in combination, a puffer cylinder disposed in an atmosphere of an interrupting gas, a fixed contact member mounted inside the cylinder, a primary piston and a secondary piston disposed inside the cylinder, a movable contact member and a vent nozzle carried by the primary piston, said movable contact member engaging the fixed contact member when the primary piston is in an end position, an accelerating spring for driving the primary piston, 21 secondary spring for driving the secondary piston from its end position to compress gas between the pistons and force gas through said nozzle, and said secondary piston being returned to its initial end position by the compressed gas.

7. In a circuit interrupter, in combination, a puffer cylinder disposed in an atmosphere of an interrupting gas, a fixed contact member mounted inside the cylinder, a primary piston and a secondary piston disposed inside the cylinder, a movable contact member and a vent nozzle carried by the primary piston, said movable contact member engaging the fixed contact member when the primary piston is in an end position, an accelerating spring for driving the primary piston, a secondary spring for driving the secondary piston from its end position to compress gas between the pistons and force gas through said nozzle, said secondary piston being returned to its initial end position by the compressed gas, latching means for retaining the secondary piston in its initial end position, and releasing means movable with the primary piston for releasing said latching means.

8. In a circuit interrupter, in combination, a puffer cylinder disposed in an atmosphere of an interrupting gas, a fixed contact member mounted inside the cylinder, a primary piston and a secondary piston disposed inside the cylinder, a movable contact member and a vent nozzle carried by the primary piston, said movable contact member engaging the fixed contact member when the primary piston is in its end position, an accelerating spring for driving the primary piston, a secondary spring for driving the secondary piston from its initial end position to compress gas between the pistons and force gas through said nozzle, and said secondary piston being returned to its initial end position by the compressed gas, pivoted latch means for retaining the secondary piston in its initial end position, hook means pivotally attached to the latch means, and release means movable with the primary piston to engage the hook means to release the latch means.

9. In a circuit interrupter, in combination, a puffer cylinder disposed in an atmosphere of an interrupting gas, a fixed contact member mounted inside the cylinder, a primary piston and a secondary piston disposed inside the cylinder, a movable contact member and a vent nozzle carried by the primary piston, said movable contact member engaging the fixed contact member when the primary piston is in its end position, an accelerating spring for driving the primary piston, a secondary spring for driving the secondary piston from its initial end position to compress gas between the pistons and force gas through said nozzle, said secondary piston being returned to its initial end position by the compressed gas, and valve means controlling the admission of gas into said cylinder.

10. In a circuit interrupter, in combination, a putter cylinder disposed in an atmosphere of an interrupting gas, a fixed contact member mounted inside the cylinder, a primary piston and a secondary piston disposed inside the cylinder, a movable contact member and a vent nozzle carried by the primary piston, said movable contact member engaging the fixed contact member when the primary piston is in its end position, an accelerating spring for driving the primary piston, a secondary spring for driving the secondary piston from its initial end position to compress gas between the pistons and force gas through said nozzle, said secondary piston being returned to its initial end position by the compressed gas, valve means controlling the admission of gas into said cylinder, and valve means in the secondary piston cooperating with the first-named valve means to cushion the return of the secondary piston to its lowermost position.

11. A circuit breaker comprising a tank containing an interrupting gas, circuit interrupting means including a hollow contact member disposed inside the tank, a puffer cylinder, a primary piston and a secondary piston disposed inside the cylinder, an accelerating spring for driving the primary piston in one direction from an initial position, a secondary spring for driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons and force gas into the hollow contact member, said secondary piston being returned to its initial position by the compressed gas, and means for returning the primary piston to its initial position and compressing the accelerating spring.

12. A circuit breaker comprising a tank containing an interrupting gas, circuit interrupting means including a hollow contact member disposed inside the tank, a putter cylinder, a primary piston and a secondary piston disposed inside the cylinder, an accelerating spring for driving the primary piston in one direction from an initial position, a secondary spring for driving the secondary piston toward the primary piston from an initial position to compress gas between the pistons and force gas into the hollow contact member, said secondary piston being returned to its initial position and the secondary spring compressed by the compressed gas, latching means for retaining the secondary piston in said initial position, means for returning the primary piston to its initial position to compress the accelerating spring, and release means actuated by movement of the primary piston away from its initial position for releasing said latching means.

13. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, piston means movably mounted on the conducting member, spring means for driving said piston means in one direction from an initial position, gascompressing means cooperating with the piston means to compress an interrupting gas between the piston means and the compressing means, and operating means for driving the compressing means and the conducting member and the movable contact in a direction opposite to the direction in which the piston means is driven by the spring means.

14. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an are, a movable conducting member attached to said movable contact, piston means movably mounted on the conducting member, spring means for driving said piston means in one direction from an initial position, gas-compressing means cooperating with the piston means to compress an interrupting gas between the piston means and the compressing means, operating means for driving the compressing means and the conducting member and the movable contact in a direction opposite to the direction in which the piston means is driven by the spring means, said piston means being returned to its initial position by the compressed gas, and latching means for releasably retaining the piston means in its initial position.

15. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, piston means movably mounted on the conducting member, spring means for driving said piston means in one direction from an initial position, gas-compressing means cooperating with the piston means to compress an interrupting gas between the piston means and the compressing means, operating means for driving the compressing means and the conducting member and the movable contact in a direction opposite to the direction in which the piston means is driven by the spring means, said piston means being returned to its initial position by the compressed gas, latching means for releasably retaining the piston means in its initial position, and means actuated by movement of the conducting member for releasing the latching means.

16. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, a putter cylinder movable with the conducting member, a piston movably mounted on the conducting member inside the putter cylinder, spring means for driving the piston in one direction from an initial position, operating means for driving the cylinder in the opposite direction to compress an interrupting gas within the cylinder, said piston being returned to its initial position by the compressed gas, and latching means for releasably retaining the piston in its initial position.

17. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, a putter cylinder movable with the conducting member, a piston movably mounted on the conducting member inside the puffer cylinder, spring means for driving the piston in one direction from an initial position, operating means for driving the cylinder in the opposite direction to compress an interrupting gas within the cylinder, said piston being returned to its initial position by the compressed gas, latching means for releasably retaining the piston in its initial position, and means actuated by movement of the conducting member for releasing the latching means.

18. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, a puffer cylinder movable with theconducting member, a piston movably mounted on the conducting member inside the puifer cylinder, spring means for driving the piston in one direction from an initial position, operating means for driving the cylinder in the opposite direction to compress an interrupting gas Within the cylinder, said piston being returned to its initial position by the compressed gas, latching means for releasably retaining the piston in its initial position, means actuated by movement of the conducting member for releasing the latching means, valve means for controlling the admission of gas into the cylinder, and additional valve means in the piston cooperating with the first-named valve means to cushion the return of the piston to its initial position.

19. A circuit interrupter of the gas-blast type comprising a relatively stationary contact, a movable contact separable from the stationary contact to establish an arc, a movable conducting member attached to said movable contact, a puffer cylinder movable with the conducting member, a piston movably mounted on the conducting member inside the puffer cylinder, spring means for driving the piston in one direction from an initial position, operating means for driving the cylinder in the opposite direction to compress an interrupting gas within the cylinder, said piston being returned to its initial position by the compressed gas, latching means for releasably retaining the piston in its initial position, means actuated by movement of the conducting member for releasing the latching means, and guide means for guiding the movement of the cylinder and the conducting member.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner.

ROBERT S. MACON, Examiner. 

1. A CIRCUIT BREAKER COMPRISING A TANK CONTAINING AN INTERRUPTING GAS, AT LEAST TWO INTERRUPTER UNITS DISPOSED INSIDE THE TANK, A CONDUCTING CROSS ARM FOR CONNECTING THE INTERRUPTER UNITS IN SERIES, EACH INTERRUPTER UNIT COMPRISING A CYLINDER, A PRIMARY PISTON AND A SECONDARY PISTON DISPOSED INSIDE THE CYLINDER, AN ACCELERATING SPRING FOR DRIVING THE PRIMARY PISTON IN ONE DIRECTION FROM AN INITIAL POSITION, A SECONDARY SPRING FOR DRIVING THE SECONDARY PISTON TOWARD THE PRIMARY PISTON FROM AN INITIAL POSITION TO COMPRESS GAS BETWEEN THE PISTON, SAID SECONDARY PISTON BEING RETURNED TO ITS INITIAL POSITION BY THE COMPRESSED GAS, AND MEANS FOR RAISING THE CROSS ARM TO COMPRESS THE ACCELERATING SPRING AND RETURN THE PRIMARY PISTON TO ITS INITIAL POSITION. 